1. Field
Aspects of the present disclosure relate to a flexible battery and a flexible electronic device including the same, and more particularly, to a flexible battery including a plurality of unit cells that are in sliding contact with each other as well as a flexible electronic device including the flexible battery as a power source.
2. Description of the Related Art
Typical batteries do not have sufficient flexibility even when they include a flexible electrode and/or a flexible external casing, so it is difficult to bend the batteries. Also, even if such typical batteries can be bent, their performance considerably deteriorates.
JP 2,570,162 discloses an electrode having a structure in which active material particles are fixed on a current collector by a conductive adhesive layer. In such an electrode, the active material particles are not easily detached from the current collector even though the electrode is bent. JP 2,698,145 discloses a thin secondary battery including a sheet electrode including a rubber-like porous sheet with which a conducting agent is mixed and a conductive polymer synthesized in voids in the porous sheet. Since such an electrode includes the rubber-like porous sheet, the electrode has excellent flexibility. JP 2002-343340 discloses an electrode having high flexibility due to designed holes formed in a positive active material layer. However, the foregoing documents only disclose techniques of preventing detachment of an active material layer caused by bending of an electrode of a battery or only disclose improving flexibility of an electrode without improving flexibility of the entire battery. In addition, the foregoing documents cannot provide means of maintaining uniform contacts between a positive electrode and a negative electrode, and/or uniform alignments thereof to perform stable electrochemical reactions when the batteries are bent.
KR 2002-0017973 discloses a battery including an electrode formed on a current collector that incorporates carbon fiber and a metal thin film in sliding contact with the electrode, in which the battery structure is sealed under reduced pressure in an external casing. In this case, while flexibility of the battery is improved by the sliding contact, flexibility is not sufficiently improved because friction between the carbon fiber current collector and the metal thin film is not sufficiently low and the battery structure is sealed under the reduced pressure. In addition, if the battery is repeatedly folded and unfolded, the contact between the carbon fiber current collector and the metal thin film may lose uniformity, thereby leading to deterioration of the battery performance.
Furthermore, a battery is generally prepared by stacking or winding a thin electrode and other elements of the battery to obtain sufficient capacity according to the purpose for use. However, if the thickness of the battery increases, flexibility of the battery decreases, making it difficult to bend the battery.